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OS Command Injection in Totolink A7100RU setIpv6LanCfg
CVE-2026-5853 is an OS command injection vulnerability affecting Totolink A7100RU firmware version 7.4cu.2313_b20191024. The flaw is present in the setIpv6LanCfg function exposed through the /cgi-bin/cstecgi.cgi CGI handler. According to the available information, insufficient sanitization of the addrPrefixLen argument allows attacker-controlled input to be incorporated into operating system command execution. The issue is remotely exploitable, and public exploit disclosure is available. The weakness is reported under CWE-78 and also referenced as CWE-77.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation allows a remote attacker to inject and execute arbitrary OS commands on the affected device. Given the reported CVSS vectors and the nature of command injection on a router appliance, this can result in full compromise of the device, including unauthorized modification of configuration, disruption of services, and access to or manipulation of data handled by the router, with high confidentiality, integrity, and availability impact.
If you can’t patch tonight, do this now.
Until a patched firmware version is confirmed, restrict remote access to the device management interface and specifically to the CGI endpoint /cgi-bin/cstecgi.cgi. Limit administrative access to trusted management networks only, disable WAN-side administration if enabled, and use network segmentation or ACLs to prevent untrusted hosts from reaching the web management plane. Monitor for suspicious requests targeting setIpv6LanCfg or the addrPrefixLen parameter, and consider replacing or isolating affected devices if exposure cannot be reduced.
Patch, then assume compromise.
Upgrade to a vendor-fixed firmware release if one becomes available from Totolink. Because the provided content identifies a specific affected firmware version but does not specify a patched version, the exact fixed release is currently not available. Review vendor advisories and apply the latest supported firmware for the A7100RU as soon as possible.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.